The present invention relates generally to a method and apparatus for collecting airborne particles, and more specifically to a slit impaction air sampler that allows for more precise analysis of collected airborne particles.
Obtaining accurate samples of airborne particles such as mold spores, pollen, skin fragments, insect parts, various fibers, and other aeroallergens is necessary or desirable for a number of different purposes, including reliable contamination studies. For example, environmental professionals need accurate samples to determine the presence and quality of deleterious such as asbestos fibers in the air. Furthermore, aero-biologists and allergists need accurate samples to identify and quantify airborne pollen and mold spore concentrations for patient diagnosis. Moreover, epidemiologists require accurate samples to determine the presence of particles carrying bacteria, such as that responsible for Legionnaire""s Disease, in air-conditioning systems and the like.
Various sampling methods and techniques are well known for use in providing particle analysis in a variety of different areas and applications. One such sampling method is filter sampling, which is well known for use in particle and fiber analysis. With filter sampling methods, air is drawn through a microporous filter as is known and the filter can then be examined under a microscope to determine the type and concentration of particles trapped on the filter. While effective for some purposes, filter sampling is time consuming and provides only limited reliability. For example, large particles such as pollen, often do not remain attached to the filter, separating therefrom during transportation and handling.
Slit or impaction samplers, which direct air at relatively high velocity through a narrow rectangular slit against a tacky material have a number of advantages over filter sampling. With slit air samplers, samples sufficient for analysis can be obtained in minutes rather than hours, the area to be examined is much smaller than the areas provided with filters, and the tacky nature of the material used to collect the sample will retain large particles better than filters. However, the configuration of these designs does not always ensure the desired accurate particle accumulation. Moreover, these samplers typically can only be used in an upright or fixed position and cannot be easily used in confined or restricted spaces because of their relatively large size.
One current sampler, which is described in U.S. Pat. No. 5,693,895, attempts to solve some of these problems by providing a smaller system with a removable sampling cell that minimizes handling of the slide at the sampling site. This sampler, however, requires the usage of a new sampling cell for each sampling run, thereby making it relatively expensive. Additionally, the disclosed sampler suffers from some disadvantages in airflow into the sampler that can lead to an incomplete gathering of air particles and therefore affect any conclusions drawn from an analysis thereof.
It is therefore an object of the present invention to provide a slit impaction sampling device that allows for the complete collection of a variety of airborne particulates for subsequent analysis.
It is a further object of the present invention to provide a slit impaction sampling device that creates a laminar flow for a more defined impaction trace, which allows for a more precise analysis.
It is still another object of the present invention to provide a slit impaction sampling device that allows for inline calibration during operation to account for pressure drops.
It is yet another object of the present invention to provide a slit impaction sampling device that is reusable.
In accordance with the above and the other objects of the present invention, a slit impaction sampling device is provided. The sampler includes a base with a microscope slide disposed thereon. The microscopic slide has an adhesive media located thereon to assist in adhering airborne particles on the microscopic slide. The base has a top cap secured thereto. The top cap has an inlet opening formed therethrough. The inlet opening has an outer venturi section and an inner laminar section that directs the air flow through the inlet opening into contact with the adhesive media such that the airborne particles form an impaction trace thereon. The air then flows around the microscope slide into an outlet passage and to a vacuum source.
These and other features of the present invention will become apparent from the following description of the invention, when reviewed in accordance with the accompanying drawings and appended claims.